The Animal Core will serve as a resource to supply Center investigators with the necessary animals and animal research techniques to effectively execute their research. The Animal Core will be responsible for the purchasing and inventory of the animals used by Center investigators, as well as, providing investigators with the technical ability required in the manipulation of the various animal models. In the past the Animal Core was responsible for the generation of genetically engineered mice. However, the focus of the research in this center application will be on investigation of endometrial biology in mouse models already generated. Therefore, the emphasis of this Core in the renewal will be to serve as a repository for the animals used in the core and for the phenotypic analysis of impact of the genetic alterations on mouse reproductive biology. This Core will incorporate the use of xenotransplants of human endometrial tissue into NOD/SCID/yc nu" (NOG) mice, as well as, the use of mouse models for endometriosis. The Core will be responsible for the execution of these complicated techniques for the analysis of endometrial biology and will only generate new models as deemed necessary. The Core will serve Center Investigators by accomplishing the following tasks: 1. The Animal Core will provide the phenotypic analysis of the impact of specific genetic alterations on mouse reproductive biology. 2. The Animal Core will conduct xenograft procedures involved in the reconstitution of endometrial tissue into mice. 3. The Animal Core will manage the colonies of genetically engineered mice for Center Investigators. 4. The Animal Core will produce mutant mice by microinjecting genetically engineered Embryonic Stem cells into the blastocoel of the embryonic day 3.5 mouse embryos and transgenic mice by DNA microinjection into the male pronucleus of one-cell mouse embryos.